146 ANNALS NEW YORK ACADEMY OF SCIENCES 



ventral lobe almost angular at the middle in some sutures, a broad, moderately 

 deep lateral lobe, the point of greatest convexity being below or interior to the 

 middle, and a gently curved internal or dorsal lobe across the impressed zone. 

 Abruptly rounded saddles occupy the ventrolateral angles and a broad saddle 

 flattened across the middle, each of the umbilical zones. Each of the latter, 

 however, may be regarded as composed of two obscure saddles, one on the 

 umbilical shoulder and one on the angle of the impressed zone with a scarcely 

 perceptible lobe between. 



The sculpture is not well shown. On the ventrolateral angles and tubercles 

 it consists of regular, strong, sharp, transverse lirre. which are deeply curved, 

 suggesting a broad, deep hyponomic sinus. 



The test appears to be considerably thickened at the ventrolateral angles so 

 that the internal mold differs appreciably from the perfect shell, the .shell 

 being flatter across the ventral surface, with the sides more convergent toward 

 the umbilicus, and with the tubercles very much more produced. Indeed, on 

 the internal mold, the tubercles are not at all prominent. 



Horizon and locality : "Wewoka formation ; Coalgate quadrangle, We- 

 woka quadrangle, Okla. 



Metacoceras cornutum var. sinuosum var. now 



A single fragmentary specimen which retains the shell is all that represents 

 this variety. It is smaller than the original species and with a less transverse 

 cross-section. The nodes are rounded instead of compressed and extend part 

 way down the sides as low, broad, obscure plications which fall far short of 

 the umbilical shoulder. The latter is regularly rounded and although strongly 

 turned, not angulated. The ventral surface is marked by two obscure sulci 

 with a gentle convexity between. The tubercles appear to be nearly opposite. 



The surface is almost smooth, the incremental lines being obscure except on 

 the tubercles, where they develop into regular, fine, though sharp line. They 

 make a deep sinus on the ventral surface, are nearly straight and gently 

 sloped backward at the sides, with a gradual change of the direction at the um- 

 bilical shoulder, beyond which on the umbilical zone they are gently concave. 



Horizon and locality : Wewoka formation ; Wewoka quadrangle, Okla. 



Metacoceras cornutum var. carinatum var. nov. 



This variety is represented by two fragments which apparently show the 

 chamber of habitation, but do not retain the septa. They are partly testifer- 

 ous and partly exfoliated. 



The variety carinatum is distinguished from either of the preceding by its 

 more rapid expansion and more transverse shape, in which it exceeds even the 

 original species itself. The sides are in consequence relatively very narrow. 

 The tubercles are rounded as in the variety sinuosum, but owing to the short- 

 ness of the sides they make more prominent plications. The ventral surface is 

 rather strongly rounded and without sulci. The umbilical shoulder is very 

 angular and extended into a crest or carina,— in which a marked diffeience is 



